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BACKGROUND AND OBJECTIVE: Inadequate postintubation sedation (PIS) can lead to unplanned extubations, conscious paralysis, and overall unsafe care of patients. From 2018 to 2020, we realized at our hospital that â¼25% of children received sedation in an adequate time frame in the pediatric emergency department, with 2 unplanned dislodgements of the endotracheal tube. Our objective was to reduce time to initiating PIS from a mean of 39 minutes to less than 15 minutes in our pediatric emergency department by September 2021. METHODS: A multidisciplinary team was formed in March 2020 to develop a key driver diagram and a protocol to standardize PIS. Baseline data were obtained from December 2017 through March 2020. The primary measure was time from intubation to administration of first sedation medication. Plan-do-study-act cycles informed interventions for protocol development, awareness, education, order set development, and PIS checklist. The secondary measure was unplanned extubations and the balancing measure was PIS-related hypotension requiring pressors. An X-bar and S chart were used to analyze data. RESULTS: Protocol implementation was associated with decrease in mean time to PIS from 39 minutes to 21 minutes. Following educational interventions, order set implementation, and the addition of PIS plan to the intubation checklist, there was a decrease in mean time to PIS to 13 minutes, which was sustained for 9 months without any observed episodes of PIS-related hypotension or unplanned extubations. CONCLUSIONS: Quality improvement methodology led to a sustained reduction in time to initiation of PIS in a pediatric emergency department.
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Anestesia , Hipotensão , Criança , Humanos , Intubação Intratraqueal/efeitos adversos , Intubação Intratraqueal/métodos , Serviço Hospitalar de Emergência , Sedação ConscienteRESUMO
Background: Croup encounters substantially decreased when the pandemic first began, specifically between March and September 2020, before croup cases dramatically spiked again with the Omicron variant. There is a dearth of information concerning children at risk for severe or refractory COVID-19-associated croup and their outcomes. Objective: The objective of this case series was to describe the clinical characteristics and outcomes of croup associated with the Omicron variant in children, with a focus on cases refractory to treatment. Methods: The case series includes children from birth to 18 years old who presented to a freestanding children's hospital emergency department in the Southeastern United States between December 1, 2021 and January 31, 2022 with a diagnosis of croup and a laboratory-confirmed diagnosis of COVID-19. We used descriptive statistics to summarize patient characteristics and outcomes. Results: Of the total 81 patient encounters, 59 patients (72.8%) were discharged from the ED, with one patient requiring two revisits to the hospital. Nineteen patients (23.5%) were admitted to the hospital, and three of these patients represented to the hospital after discharge from the hospital. Three patients (3.7%) were admitted to the intensive care unit, none of whom represented after discharge. Conclusions: This study reveals a wide age range of presentation as well as a relatively higher rate of admission and fewer coinfections compared to pre-pandemic croup. Reassuringly, the results also show a low postadmission intervention rate as well as a low revisit rate. We discuss four refractory cases to highlight nuances for management and disposition decisions.
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Successful publication of quality improvement (QI) work is predicated on the use of established QI frameworks and rigorous analytical methods that allow teams to understand the impact of interventions over time. This article is meant to help QI teams disseminate their work more broadly through publication by providing tangible methods that many journals desire in QI articles with specific examples of published works referenced throughout the article. We introduce improvement frameworks that teams should identify early and use as a foundation throughout their projects. We review vital aspects of QI projects, such as team formation, creation of a succinct and clear aim statement, defining primary, process, and balancing measures, as well as QI tools like key driver diagrams, Ishikawa (fishbone) diagrams, and Pareto charts. Finally, we highlight the importance of analyzing data over time to understand the impacts of plan-do-study-act cycles on data. Annotated run charts or, more preferably, annotated statistical process control (or Shewhart) charts are both statistically sound methods to identify significant changes over time. Deliberate planning and execution of QI projects using these concepts will lead to improved chances of QI teams finding success in their project and eventual article acceptance.
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Melhoria de Qualidade , HumanosRESUMO
BACKGROUND: Previous interventions to reduce emergency department (ED) overutilization from non-urgent visits have shown little success. At our hospital, we created an ED to primary care clinic (PCC) transfer protocol for non-urgent ED visits of established patients. Our study analyzed the impact of this protocol on patient encounters. METHODS: Chart reviews were conducted for a retrospective cohort of transfers from the ED to PCC from 9/01/17-8/31/18. Primary outcomes included length of stay (LOS), cost, and need for return to the ED. Cost savings were calculated by comparing encounters with identical primary diagnoses in the ED with internal technical and professional financial data. Secondary outcomes were final diagnoses and primary care services provided. RESULTS: 374 patient encounters were transferred from ED to PCC. The five most common diagnoses were viral upper respiratory infection (n=80, 21.4%), dermatologic diagnoses (n=37, 9.9%), acute otitis media (n=35, 9.4%), pharyngitis (n=34, 9.1%), and influenza (n=34, 9.1%). Overall, total cost savings equaled approximately $100,000. For the top 10 diagnoses, costs were reduced from $29-$46 per $100 of ED costs and LOS was reduced by a mean of 49 min/encounter. For 9 of these 10 conditions, costs exceeded reimbursement in both settings; however, evaluation in PCC versus ED reduced the loss of revenue by 10-68%. Sixty-four encounters (17.1%) received additional primary care services. There were no safety events or inappropriate transfers. CONCLUSIONS: This protocol provided a safe, efficient method for patients to be evaluated in their medical home while reducing non-urgent emergency visits in the ED. LEVEL OF EVIDENCE: VI.
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Serviço Hospitalar de Emergência , Atenção Primária à Saúde , Criança , Redução de Custos , Humanos , Tempo de Internação , Estudos RetrospectivosRESUMO
BACKGROUND: Clinician documentation is highly variable, and awareness of documentation requirements remains low despite post-training experience. At our hospital, critical care (CC) documentation was inconsistent. Our aim was to increase appropriate CC attestations from 51% to 90% for status asthmaticus, anaphylaxis, and diabetic ketoacidosis in the pediatric emergency department by December 2021. METHODS: A physician team developed a key driver diagram. Retrospective baseline data using International Classification of Diseases, Ninth and Tenth Revision codes were obtained from January 2018 to September 2020, after which data were followed prospectively in consecutive groups of 20 encounters. Statistical process control charts were used to analyze data. Nelson rules were used to detect special cause variation. Primary outcome was the inclusion of appropriate CC attestations. Interventions included education, CC attestation templates, and provider feedback. We also tracked charges for the 3 diagnoses studied. Process measures included template use. Balancing measure was refusal of payment by insurers. RESULTS: P-charts were used to analyze primary outcome and process measures. X-bar charts were used to analyze charges. Baseline data represented 706 encounters with 51% including CC documentation. Following clinician education and release of the CC template, special cause variation was detected, and centerline shifted to 88.1% (Fig 2). Average charges per encounter increased from $4527 to $5385. There was no reported refusal of payment. CONCLUSIONS: We successfully achieved improvements in CC documentation in the 3 diagnoses of interest through education and process changes in documentation, leading over $1 million in new charges over the past 15 months.
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Documentação , Serviço Hospitalar de Emergência , Criança , Cuidados Críticos , Humanos , Classificação Internacional de Doenças , Estudos RetrospectivosRESUMO
We use single photon detectors to probe the motional state of a superfluid ^{4}He resonator of mass â¼1 ng. The arrival times of Stokes and anti-Stokes photons (scattered by the resonator's acoustic mode) are used to measure the resonator's phonon coherences up to the fourth order. By postselecting on photon detection events, we also measure coherences in the resonator when ≤3 phonons have been added or subtracted. These measurements are found to be consistent with predictions that assume the acoustic mode to be in thermal equilibrium with a bath through a Markovian coupling.
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BACKGROUND AND OBJECTIVES: Bronchiolitis is a leading cause of pediatric hospitalization in the United States, resulting in significant morbidity and health care resource use. Despite American Academy of Pediatrics recommendations against obtaining chest radiographs (CXRs) for bronchiolitis, variation in care continues. Historically, clinical practice guidelines and educational campaigns have had mixed success in reducing unnecessary CXR use. Our aim was to reduce CXR use for children <2 years with a primary diagnosis of bronchiolitis, regardless of emergency department (ED) disposition or preexisting conditions, from 42.1% to <15% of encounters by March 2020. METHODS: A multidisciplinary team was created at our institution in 2012 to standardize bronchiolitis care. Given success with higher reliability interventions in asthma, similar interventions affecting workflow were subsequently pursued with bronchiolitis, starting in 2017, by using quality improvement science methods. The primary outcome was the percent of bronchiolitis encounters with a CXR. The balancing measure was return visits within 72 hours to the ED. Statistical process control charts were used to monitor and analyze data obtained from an internally created dashboard. RESULTS: From 2012 to 2020, our hospital had 12 120 bronchiolitis encounters. Preimplementation baseline revealed a mean of 42.1% for CXR use. Low reliability interventions, like educational campaigns, resulted in unsustained effects on CXR use. Higher reliability interventions were associated with sustained reductions to 23.3% and 18.9% over the last 4 years. There was no change in ED return visits. CONCLUSIONS: High-reliability workflow redesign was more effective in translating American Academy of Pediatrics recommendations into sustained practice than educational campaigns.
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Bronquiolite/diagnóstico , Uso Excessivo dos Serviços de Saúde/prevenção & controle , Melhoria de Qualidade/organização & administração , Radiografia Torácica/estatística & dados numéricos , Pré-Escolar , Serviço Hospitalar de Emergência/estatística & dados numéricos , Hospitais Pediátricos , Humanos , Equipe de Assistência ao Paciente , TennesseeRESUMO
Metachromatic leukodystrophy (MLD) is an autosomal recessive lysosomal storage disease mainly caused by a deficiency of arylsulfatase A activity. The typical clinical course of patients with the late infantile form includes a regression in motor skills with progression to dysphagia, seizures, hypotonia and death. We present a case of a 4-year-old female with rapidly progressive developmental regression with loss of motor milestones, spasticity and dysphagia. MRI showed volume loss and markedly abnormal deep white matter. Enzymatic testing in one laboratory showed arylsulfatase A activity in their normal range. However, extraction of urine showed a large increase in sulfatide excretion in a second laboratory. Measurement of arylsulfatase A in that laboratory showed a partial decrease in arylsulfatase A activity measured under typical conditions (about 37% of the normal mean). When the concentration of substrate in the assay was lowered to one quarter of that normally used, this individual had activity <10% of controls. The patient was found to be homozygous for an unusual missense mutation in the arylsulfatase A gene confirming the diagnosis of MLD. This case illustrates the importance of careful biochemical and molecular testing for MLD if there is suspicion of this diagnosis.
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BACKGROUND: Computed tomography (CT) is frequently used to identify intra-abdominal injuries in children with blunt abdominal trauma (BAT). The Pediatric Emergency Care Applied Research Network (PECARN) proposed a prediction rule to identify children with BAT who are at very low risk for clinically-important intra-abdominal injuries (CIIAI) in whom CT can be avoided. OBJECTIVE: To determine the sensitivity of this prediction rule in identifying patients at very low risk for CIIAI in our pediatric trauma registry. METHODS: Retrospective review of our institutional trauma registry to identify patients with CIIAI. CIIAI included cases resulting in death, therapeutic intervention at laparotomy, angiographic embolization of intra-abdominal arterial bleeding, blood transfusion for intra-abdominal hemorrhage, and administration of intravenous fluids for two or more nights for pancreatic or gastrointestinal injuries. Patients were identified using ICD diagnosis and procedure codes. Kappa was calculated to evaluate inter-reviewer agreement. RESULTS: Of 5743 patients, 133 (2.3%) had CIIAI. 60% were male and the mean age was 8 (SD 4.4) years. One patient with CIIAI met the proposed very low risk criteria, resulting in a prediction rule sensitivity of 99%, 95% CI [96-100%]. This patient also had extra-abdominal arterial bleeding requiring revascularization, offering an alternative reason for transfusion. Kappa was 0.85, 95% CI [0.82, 0.89], indicating strong inter-rater agreement. CONCLUSIONS: One out of 133 patients with CIIAI met very low risk criteria based on the PECARN prediction rule. This study supports the PECARN clinical prediction rule in decreasing CT use in pediatric patients at very low risk for CIIAI.
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Traumatismos Abdominais/diagnóstico , Regras de Decisão Clínica , Ferimentos não Penetrantes/diagnóstico , Traumatismos Abdominais/diagnóstico por imagem , Acidentes de Trânsito , Transfusão de Sangue , Criança , Pré-Escolar , Feminino , Hidratação , Fraturas Ósseas/diagnóstico , Fraturas Ósseas/diagnóstico por imagem , Fraturas Ósseas/terapia , Hematoma/diagnóstico , Hematoma/diagnóstico por imagem , Hematoma/terapia , Humanos , Intestinos/lesões , Intestinos/cirurgia , Laparotomia , Fígado/lesões , Fígado/cirurgia , Masculino , Ossos Pélvicos/lesões , Ossos Pélvicos/cirurgia , Estudos Retrospectivos , Medição de Risco , Fraturas da Coluna Vertebral/diagnóstico , Fraturas da Coluna Vertebral/diagnóstico por imagem , Fraturas da Coluna Vertebral/terapia , Baço/lesões , Baço/cirurgia , Tomografia Computadorizada por Raios X , Ferimentos não Penetrantes/diagnóstico por imagemAssuntos
Bacteriemia/diagnóstico , Bacteriemia/terapia , Pneumonia Bacteriana/diagnóstico , Pneumonia Bacteriana/terapia , Pielonefrite/terapia , Infecções Estreptocócicas/diagnóstico , Antibacterianos/uso terapêutico , Criança , Terapia Combinada/métodos , Progressão da Doença , Serviço Hospitalar de Emergência , Hidratação/métodos , Seguimentos , Humanos , Lactente , Masculino , Pielonefrite/diagnóstico , Medição de Risco , Estudos de Amostragem , Índice de Gravidade de Doença , Infecções Estreptocócicas/tratamento farmacológico , Resultado do TratamentoRESUMO
Despite numerous published studies describing adjuvant chemotherapy for canine appendicular osteosarcoma, there is no consensus as to the optimal chemotherapy protocol. The purpose of this study was to determine whether either of two protocols would be associated with longer disease-free interval (DFI) in dogs with appendicular osteosarcoma following amputation. Dogs with histologically confirmed appendicular osteosarcoma that were free of gross metastases and underwent amputation were eligible for enrollment. Dogs were randomized to receive either six doses of carboplatin or three doses each of carboplatin and doxorubicin on an alternating schedule. Fifty dogs were included. Dogs receiving carboplatin alone had a significantly longer DFI (425 versus 135 days) than dogs receiving alternating carboplatin and doxorubicin (P = 0.04). Toxicity was similar between groups. These results suggest that six doses of carboplatin may be associated superior DFI when compared to six total doses of carboplatin and doxorubicin.
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Neoplasias Ósseas/veterinária , Carboplatina/uso terapêutico , Doenças do Cão/tratamento farmacológico , Doxorrubicina/uso terapêutico , Osteossarcoma/veterinária , Animais , Antineoplásicos/administração & dosagem , Antineoplásicos/uso terapêutico , Neoplasias Ósseas/tratamento farmacológico , Carboplatina/administração & dosagem , Quimioterapia Adjuvante , Cães , Doxorrubicina/administração & dosagem , Osteossarcoma/tratamento farmacológicoRESUMO
This retrospective case series evaluates the outcome of 21 dogs with grade II stage 2 mast cell tumour (MCT) treated with adequate local therapy and adjuvant systemic chemotherapy (prednisone, vinblastine and CCNU). The median survival for all dogs was 1359 days (range, 188-2340). Median disease-free interval was 2120 days (149-2325 days). Dogs treated with surgery and chemotherapy had shorter survival (median, 1103 days; 188-2010 days) than those that underwent surgery, radiation therapy and chemotherapy as part of their treatment (median, 2056 days; 300-2340 days). Two patients had local recurrence in the radiation field and four patients had de novo MCT. Distant metastasis was not observed in any dogs. The results of this study suggest that, in the presence of loco-regional lymph node metastasis in grade II MCT, the use of prednisone, vinblastine and CCNU after adequate local-regional therapy can provide a median survival in excess of 40 months.
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Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Doenças do Cão/tratamento farmacológico , Lomustina/uso terapêutico , Sarcoma de Mastócitos/veterinária , Prednisona/uso terapêutico , Vimblastina/uso terapêutico , Animais , Antineoplásicos Alquilantes/farmacologia , Antineoplásicos Alquilantes/uso terapêutico , Antineoplásicos Hormonais/farmacologia , Antineoplásicos Hormonais/uso terapêutico , Antineoplásicos Fitogênicos/farmacologia , Protocolos de Quimioterapia Combinada Antineoplásica/farmacologia , California , Intervalo Livre de Doença , Doenças do Cão/patologia , Cães , Feminino , Lomustina/farmacologia , Linfonodos/patologia , Masculino , Sarcoma de Mastócitos/tratamento farmacológico , Sarcoma de Mastócitos/patologia , Estadiamento de Neoplasias , Prednisona/farmacologia , Estudos Retrospectivos , Vimblastina/farmacologiaRESUMO
Rosiglitazone is an FDA-approved peroxisome proliferator-activated receptor gamma (PPARγ) agonist and antidiabetic agent in humans that has been investigated for its ability to reduce tumor cell growth. The purpose of this study was to determine the maximally tolerated dose, peak plasma concentrations and side effect profile of oral rosiglitazone when combined with carboplatin in dogs with cancer. Rosiglitazone was administered at 6 and 8 mg/m(2) to seven dogs. Carboplatin was administered at 240-300 mg/m(2) in combination with rosiglitazone. For toxicity evaluation, the toxicity data for the seven dogs in this study were combined with the toxicity data from three dogs previously reported in a methodology study. Peak plasma rosiglitazone concentrations varied with dose. The dose-limiting toxicity was hepatic at a dose of 8 mg/m(2). Three dogs had mild to moderate alanine aminotransferase elevations but no changes in total bilirubin, alkaline phosphatase, blood glucose or γ-glutamyltranspeptidase values were noted.
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Antineoplásicos/farmacocinética , Carboplatina/farmacocinética , Doenças do Cão/tratamento farmacológico , Hipoglicemiantes/farmacocinética , Neoplasias/veterinária , Tiazolidinedionas/farmacocinética , Administração Oral , Animais , Antineoplásicos/administração & dosagem , Antineoplásicos/efeitos adversos , Antineoplásicos/uso terapêutico , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Carboplatina/administração & dosagem , Carboplatina/efeitos adversos , Carboplatina/uso terapêutico , Cães , Relação Dose-Resposta a Droga , Feminino , Hipoglicemiantes/administração & dosagem , Hipoglicemiantes/efeitos adversos , Hipoglicemiantes/uso terapêutico , Injeções Intravenosas , Masculino , Neoplasias/tratamento farmacológico , Rosiglitazona , Tiazolidinedionas/administração & dosagem , Tiazolidinedionas/efeitos adversos , Tiazolidinedionas/uso terapêuticoRESUMO
Oral fibrosarcoma (FSA) is a common oral tumour in dogs, and historically reported survival times after surgical excision range from 7.0 to 12.2 months with local recurrence rates of 32-57%. The purpose of this retrospective study was to report outcome in a cohort of dogs with oral FSA treated with surgical excision with or without adjuvant radiation therapy. Twenty-nine dogs with a histological diagnosis of FSA arising from the oral cavity that underwent surgical resection of their oral FSA were included in this study. Twenty-one dogs were treated with surgical excision alone and eight dogs with both surgery and radiation therapy. The median progression-free interval was >653 days. The median survival time was 743 days. The 1- and 2-year survival rates were 87.7 and 57.8%, respectively. Seven (24.1%) dogs developed local recurrence. Seven dogs (24.1%) developed metastasis.
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Doenças do Cão/cirurgia , Fibrossarcoma/veterinária , Neoplasias Bucais/veterinária , Animais , California/epidemiologia , Terapia Combinada/veterinária , Doenças do Cão/patologia , Doenças do Cão/radioterapia , Cães , Feminino , Fibrossarcoma/patologia , Fibrossarcoma/radioterapia , Fibrossarcoma/cirurgia , Masculino , Neoplasias Bucais/patologia , Neoplasias Bucais/radioterapia , Neoplasias Bucais/cirurgia , Recidiva Local de Neoplasia/epidemiologia , Estudos Retrospectivos , Faculdades de Medicina Veterinária , Análise de Sobrevida , Resultado do TratamentoRESUMO
Dogs with multicentric T-cell lymphoma are commonly treated with CHOP chemotherapy protocols that include cyclophosphamide, doxorubicin, vincristine and prednisone. The purpose of this study was to evaluate the use of CHOP chemotherapy for dogs with multicentric T-cell lymphoma. Identification of prognostic factors in this specific subset of dogs was of secondary interest. Twenty-three out of 24 dogs responded to CHOP chemotherapy and these dogs remained on the protocol for a median of 146 days. No variable was associated with progression free survival (PFS) including stage, substage, hypercalcemia or radiographic evidence of a cranial mediastinal mass. The median overall survival time (OST) for all dogs was 235 days. Dogs that were thrombocytopenic at presentation experienced a significantly longer OST (323 versus 212 days, P=0.01).
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Antineoplásicos/uso terapêutico , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Doenças do Cão/tratamento farmacológico , Linfoma de Células T/veterinária , Animais , Protocolos de Quimioterapia Combinada Antineoplásica/administração & dosagem , California , Ciclofosfamida/administração & dosagem , Ciclofosfamida/uso terapêutico , Intervalo Livre de Doença , Cães , Doxorrubicina/administração & dosagem , Doxorrubicina/uso terapêutico , Feminino , Linfoma de Células T/tratamento farmacológico , Masculino , Estadiamento de Neoplasias , Prednisona/administração & dosagem , Prednisona/uso terapêutico , Prognóstico , Estudos Retrospectivos , Vincristina/administração & dosagem , Vincristina/uso terapêuticoRESUMO
Sense organs in the legs that detect body weight are an important component in the regulation of posture and locomotion. We tested the abilities of tibial campaniform sensilla, receptors that can monitor forces in the cockroach leg, to encode variations in body load in freely standing animals. Small magnets were attached to the thorax and currents were applied to a coil below the substrate. Sensory and motor activities were monitored neurographically. The tibial sensilla could show vigorous discharges to changing forces when animals stood upon their legs and actively supported the body weight. Firing of individual afferents depended upon the orientation of the receptor's cuticular cap: proximal sensilla (oriented perpendicular to the leg axis) discharged to force increases while distal receptors (parallel to the leg) fired to decreasing forces. Proximal sensillum discharges were prolonged and could encode the level of load when increases were sustained. Firing of the trochanteral extensor motoneuron was also strongly modulated by changing load. In some postures, sensillum discharges paralleled changes in motor frequency consistent with a known interjoint reflex. These findings demonstrate that tibial campaniform sensilla can monitor the effects of body weight upon the legs and may aid in generating support of body load.
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Extremidades/fisiologia , Movimento/fisiologia , Postura/fisiologia , Órgãos dos Sentidos/fisiologia , Tórax/fisiologia , Suporte de Carga/fisiologia , Animais , Baratas , Relação Dose-Resposta à Radiação , Gânglios Sensitivos/fisiologia , Magnetismo , Atividade Motora , Propriocepção , Sensibilidade e EspecificidadeRESUMO
Previous studies in insects demonstrated that leg coordination changes following complete ablation of distal limb segments. However, normal coordination was restored when small 'peg leg' prostheses were attached to leg stumps to permit substrate contact. We have adapted this paradigm to preserve appropriate leg mass and inertia by severing all nerves and muscle tendons in the femur of the cockroach hind leg and converting the animal's own limb into a peg leg. Recordings of muscle activities and leg movements before and after denervation showed that: (1) the 'peg leg' is actively used in walking and regular bursts occur in motoneurons to leg extensor muscles; (2) driving of motoneuron activity is sufficient to produce 'fictive' bursting in a muscle whose tendon (apodeme) is cut in the ablation; and (3) similar motoneuron activities are found in walking on an oiled glass surface, when the effects of body weight and mechanical coupling are minimized. When distal segments were completely severed in these preparations, leg use and muscle bursting were disrupted but could be restored if the stumps were pressed against the substrate. These results support the hypothesis that feedback from receptors in proximal leg segments indicating forces allows for active leg use in walking.
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Biorretroalimentação Psicológica/fisiologia , Extremidades/fisiologia , Músculo Esquelético/fisiologia , Sensação/fisiologia , Caminhada/fisiologia , Animais , Baratas , Denervação/métodos , Eletromiografia/métodos , Extremidades/inervação , Instinto , Atividade Motora/fisiologia , Neurônios Motores/fisiologia , Contração Muscular/fisiologia , Músculo Esquelético/inervaçãoRESUMO
All animals generate progressively larger forces as they increase in size and mass. Their abilities to detect these forces must be similarly adjusted. In insects, campaniform sensilla monitor strains in the exoskeleton and provide information about forces acting upon the legs. Each sensory neuron possesses a dendrite that inserts into a cuticular cap in the exoskeleton. The cap is the site of mechanotransduction. We measured the sizes and numbers of receptor caps on the cockroach hindleg at different developmental stages. Our goal was to identify morphological features that could be correlated with the range of forces that must be detected. As cockroaches increase in size through successive molts, the number of cuticular caps in each group increases. The tibial group, for example, has two sensilla in first instar animals and 10-12 in the adult. There is also an increase in the range of cap sizes within each group. Observations of animals and their molted exoskeletons suggest that this increase occurs as the caps of existing receptors increase in size and smaller ones are added with each molt. These changes may be important in increasing the range of forces the receptors can signal while retaining sensitivity to low levels of force.
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Responses of the tibial campaniform sensilla, receptors that encode strains in the exoskeleton, were characterized by recording sensory activities during perturbations in freely standing cockroaches. The substrate upon which the animal stood was displaced horizontally using ramp and hold stimuli at varied rates. The sensilla showed short latency responses that were initiated in the first 30 ms of platform movement. Responses of individual receptors depended upon the direction of displacement and the orientation of their cuticular cap. Proximal receptors, whose caps are perpendicular to the long axis of the tibia, responded to displacements directed from the contralateral side of the body and from the head toward the abdomen. The distal sensilla, oriented parallel to the tibia, discharged at longer latency to displacements in opposite directions. Plots of receptor activity versus displacement direction showed that proximal and distal sensilla are activated in non-overlapping ranges of movement direction. Afferent responses also increased as the platform was displaced more rapidly. These results are consistent with a model in which displacements produce forces that result in bending of the tibia. This information could be utilized to detect the direction and rate of forces that occur during leg slipping or in walking on unstable terrains.
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Neurônios Aferentes/fisiologia , Periplaneta/fisiologia , Caminhada/fisiologia , Animais , Magnetismo , Masculino , Postura/fisiologia , Tempo de Reação/fisiologia , Limiar Sensorial/fisiologia , Gravação em VídeoRESUMO
Variations in intrathoracic pressure generated by different ventilator weaning modes may significantly affect intrathoracic hemodynamics and cardiovascular stability. Although several investigators have attributed cardiovascular alterations during ventilator weaning to augmented sympathetic tone, there is limited investigation of changes in autonomic tone during ventilator weaning. Heart rate variability (HRV), the analysis of beat-to-beat changes in heart rate, is a noninvasive indicator of autonomic tone that might be useful in the identification of patients who are at risk for weaning difficulty due to underlying cardiac dysfunction. The authors describe HRV and hemodynamics in response to 3 ventilatory conditions: pressure support (PS) 10 cmH2O, continuous positive airway pressure (CPAP) 10 cmH2O, and a combination of PS 10 cmH2O and CPAP 10 cmH2O (PS + CPAP) in a group of canines with normal ventricular function. Six canines were studied in the laboratory. Continuous 3-lead electrocardiographic data were collected during baseline (controlled mechanical ventilation) and following transition to each of the ventilatory conditions (PS, CPAP, PS + CPAP) for analysis of HRV. HRV was evaluated using power spectral analysis to define the power under the curve in a very low frequency range (0.0033 to < 0.04 Hz, sympathetic tone), a low frequency range (0.04 to < 0.15 Hz, primarily sympathetic tone), and a high frequency range (0.15 to < 0.40 Hz, parasympathetic tone). A thermodilution pulmonary artery catheter measured cardiac output and right ventricular end-diastolic volume to describe global hemodynamics. There were significant increases in very low frequency power (sympathetic tone) with a concomitant significant reduction in high-frequency power (parasympathetic tone) with exposure to PS + CPAP. These alterations in HRV were associated with significantly increased heart rate and reduced right ventricular end-diastolic volume. Although there was a small but significant increase in cardiac output with exposure to PS, HRV was unchanged. These data indicate that there was a relative shift in autonomic balance to increased sympathetic and decreased parasympathetic tone with exposure to PS + CPAP. The increase in intrathoracic pressure reduced right ventricular end-diastolic volume (preload). This hemodynamic alteration generated a change in autonomic tone, so that cardiac output could be maintained. Individuals with autonomic and/or cardiovascular dysfunction may not be capable of this type of response and may fail to successfully wean from mechanical ventilation.